Lab 7: Retina, Macula and Fovea, Optic Disc and Optic Nerve

Layers of the Retina

(choroid) 1. RPE 2. Photoreceptor Layer 3. OLM 4. ONL 5. OPL 6. INL 7. IPL 8. Ganglion Cell Layer 9. Nerve Fiber Layer 10. ILM (vitreous)

MAcula

-contains many cones and few rods and the cones are slightly modified -good blood supply

Outer Segment

-contains visual pigments

Optic Nerve

-formed largely by ganglion cell axons from the retina -axons are unmyelinated within the eye then become myelinated at the lamina cribosa -a.k.a. CN II -dura mater, arachnoid mater, pia mater

Optic Disc

-ganglion cell axons leaving the eye interrupt the retina and choroid in this area -the lamina cribosa crosses across this

Cones

-less numerous -density outside of the macula decreases sharply -used in high illumination and photopic vision, providing color discrimination

Rods

-more numerous than cones -no rods in the fovea -used in low illumination and responsible for scotopic vision

Blind spot

-no light sensitivity

Outer Nuclear Layer

-nuclei and cell bodies of rods and cones

Photoreceptor Layer

-outer and inner segments of rods and cones

RPE

-outermost portion of the retina -contain large amounts of pigment that absorbs light entering the eye -not part of the neural retina

Ganglion Cells

-receive the impulse from the bipolar cells -fibers of these cells then carry the visual information in the nerve fiber layer toward the optic disc

Inner Segment

-responsible for general functioning. -highly active cells

Fovea

-retina is half as thick here -only layers present ( RPE, photoreceptors, and OLM and ILM -contains only cones -highest visual acuity

Outer Plexiform Layer

-synapses between photoreceptors -contains horizontal and bipolar cells

Bipolar Cells

-these receive impulse from the rods and cones and carry it toward the ganglion cells

Retina

Light- sensitive tissue of the eye; converts light entering the eye into a nerve impulse, which is carried along the visual pathway

Paracentral Retina

a concentric band surrounding the macula

Inner Nuclear Layer

cell bodies of bipolar, horizontal, and amacrine cells

Ganglion cell layer

cell bodies of ganglion cells

Muller's Cells

cells that nourish and support other retinal cells. -extend between the outer and inner limiting membranes and play a part in their formation

Cell body

contains the nucleus of the photoreceptor

Amacrine Cells

provide communication between ganglion cells

Horizontal Cells

provide communication between photoreceptors

Inner Plexiform Layer

synapses between bipolar, ganglion, and amacrine cells

Central Retina

the macula and fovea, at the posterior pole of the eye, and the areas of the retina giving the highest resolution of objects, i.e. the highest level of visual acuity

Peripheral Retina

the most anterior portion of the retina, extending to the ora serrata

Retinal Neurons

those carrying the impulse through the thickness of the retina i.e. running vertically through the retina

visual pigments

to absorb light entering the eye and convert it into a nervous impulse

Axon

transmit impulse to bipolar and horizontal cells via the synaptic body

Red-sensitive, Green sensitive, Blue-sensitive

visual pigment in human cones

Rhodopsin

visual pigment in human rods -is purple and bleach by light. -retinal and opsin

Photoreceptors (rods and cones)

where the visual process is initiated